1. Field of the Invention
The present invention relates to an improvement in igniters for solid fuel rocket motors, and has particular application in high performance solid fuel rocket motors having full, head-end propellant webs.
2. Description of the Prior Art
The conventional igniter for large solid fuel rocket motors is a miniature rocket motor that is known in the art as a "pyrogen" igniter. Typically, a pyrogen igniter is mounted in the forward end of a motor through a hole in the propellant. In some high-performance rocket motors, however, a pyrogen igniter is impractical because of the full, head-end web of the propellant in the forward end of the motor. The head-end web propellant grain design provides a higher mass fraction; additionally, it minimizes nozzle throat size, which, in turn, maximizes the nozzle expansion ratio within the motor length envelope and minimizes insulation weight.
An igniter for such high performance rocket motors must be attached to, that is, mounted on, the forward portion of the propellant, itself, thereby to provide the ignition source of heat as close as possible to the surface to be ignited. Upon ignition of and burning of the propellant, however, the support for the igniter is eroded. This causes the igniter to become detached from the propellant and presents a problem of possible resultant damage to the rocket motor nozzle or the propellant. Therefore, in order to avoid such damage, the igniter must be substantially consumed before becoming detached from the propellant. Additionally, the igniter must perform its intended function of igniting the propellant before it is consumed.